Electric spark ignition apparatus



May 29, 1956 J. A. LAHRD 2,748,313

ELECTRIC SPARK IGNITION APPARATUS Filed June 27, 1952 Fig.1

Fig.2

United rates Patent ELECTRIC SPARK IGNITION APPARATUS John Andrew Laird, Coventry, England, assignor to Joseph Lucas (industries) Limited, Birmingham, England Application June 27, 1952, Serial No. 296,015

Claims priority, application Great Britain July 12, 1951 1 Claim. (Cl. 315-180) This invention relates to electric spark ignition apparatus for igniting combustible gas mixtures in prime movers, the apparatus being of the kind comprising a condenser (herein termed the principal condenser), and a control gap and an inductance arranged in series with the condenser, the latter receiving its charge from any convenient source, and the discharge being effected across an igniting plug.

The object of the invention is to minimise risk of failure of occurrence of the spark at the igniting plug.

The invention comprises an apparatus of the kind aforesaid, having an additional condenser connected to the inductance and arranged in parallel with the principal condenser.

The invention also comprises a resistance connected in parallel with the additional condenser.

In the accompanying drawings:

Figures land 2 respectively illustrate in diagrammatic form two embodiments of the invention.

The already known parts of the apparatus comprise a principal condenser a of the desired capacity. This condenser is intended to be charged intermittently from a magneto, ignition coil or any other convenient source. In series with the condenser is arranged a control gap b adapted to determine the voltage at which the condenser is discharged. Also in series with the control gap is arranged an inductance c, the end of the inductance remote from the control gap being adapted for connection'to the igniting plug d.

In the embodiment of the invention shown in Figure 1, an additional condenser e is arranged in parallel with the ice condenser a and has one side connected to an intermediate point of the inductance c so that the latter can perform the function of a step-up transformer, as well as its normal function of prolonging the duration of discharge of the first condenser.

In the embodiment of the invention shown in Figure 2, one electrode of the control gap [1, is connected to an intermediate point of the inductance c, and one side of the additional condenser e is connected to the end of the inductance remote from the igniting plug d.

In either arrangement a resistance 1 may be connected in parallel with the additional condenser to avoid the occurrence of a residual charge therein after each discharge.

By arrangiug an additional condenser in the manner above described, it has been found that risk of failure of the spark discharge at the igniting plug can be minimised or eliminated.

Having thus described my invention What I claim as new and desire to secure by Letters Patent is:

An electric spark ignition apparatus comprising in combination an intermittently chargeable and dischargeable principal condenser, a fixed control gap connected in series with the principal condenser to determine the voltage at which the condenser is dischargeable, a spark gap connected in series with the principal condenser and control gap, the latter being situated between the principal condenser and spark gap, an inductance connected at least in part in series with the principal condenser, control gap and spark gap, and between the control gap and spark gap, for prolonging the duration of discharge of the principal condenser across the spark gap, and an additional condenser connected in parallel with the principal condenser and in series with a part of the inductance remote from the spark gap so that the latter can serve also as a step-up transformer for initiating discharge of the principal condenser across the spark gap.

References Cited in the file of this patent UNITED STATES PATENTS 2,416,971 Welch Mar. 4, 1947 2,489,780 Hooven Nov. 29, 1949 2,551,101 Debenham et al May 1, 1951 2,571,789 Tognola Oct. 16, 1951 2,651,005 Tognola Sept. 1, 1953 

